Removing SCADA worm could disrupt power plants

Siemens has made a program available for detecting and disinfecting malware attacking its software used to control power grids, gas refineries, and factories but warned customers who use it could disrupt sensitive plant operations.

The Munich-based engineering company on Thursday began distributing Sysclean, a malware scanner made by Trend Micro. It has been updated to remove Stuxnet, a worm that spreads by exploiting two separate vulnerabilities in Siemens's SCADA, or supervisory control and data acquisition, software and every supported version of Microsoft Windows.

“As each plant is individually configured, we cannot rule out the possibility that removing the virus may affect your plant in some way,” Siemens warned. The company also advised customers to keep the scanner updated because “there are currently some new derivative versions of the original virus around.”

Stuxnet has infected the engineering environment of at least one unidentified Siemens customer, and has since been eliminated, Siemens said. So far, the company said, there are no known infections of production plants. The worm spreads whenever a system running Siemens's SCADA software is attached to an infected USB stick. The attacks use a recently documented vulnerability in the Windows shortcut feature to take control of customer PCs. Once there, the worm takes advantage of default passwords in WinCC, the SCADA software provided by Siemens.

Siemens has come under blistering criticism for not removing the vulnerability two years ago, when, according toWired.com, the default password threat first came to light.

“Siemens has put their customers at risk with this egregious vulnerability in their software,” Chris Wysopal, CTO of application security tools firm Veracode, wrote Thursday. “Worse, in my book however, is all the customers who purchased the software not knowing of its risk. Software customers that are operating SCADA systems on critical infrastructure or their factories with the WinCC software had a duty to their customers and shareholders to not purchase this software without proper security testing.”

Siemens has updated WinCC to fix the vulnerability. Microsoft has issued a stopgap fix but hasn't said yet when it plans to patch the the Windows bug. ®